You're right about Elizabeth's character not being very prominent in the movie. It makes me wonder if Elizabeth will sell as well as Nellie did last Christmas. But the movie is not centered around Felicity's and Elizabeth's friendship. It is basically Felicity's story as written in the six Felicity books. Julia Roberts announced she was going to produce the movies and AG decided to capitalize with the friends dolls.

I do think the Samantha movie was much more about her relationship with Nellie than her books were. I didn't find Nellie to be such a prominent character in the stories, except the last one, but she was definitelly a main character in the movie.